1. Field of the Invention
The present invention relates to an abrasion-resistant bumper for a nail-driving tool.
2. Description of the Related Art
U.S. Pat. No. 4,932,480 to Golsch issued on Jun. 12, 1990 discloses a pneumatically powered nail-driving tool 10 comprising a cylinder 20, a piston 26 reciprocatingly received in the cylinder 20, and a main valve 60 for driving the piston 26. A driving element 32 is attached to the piston 26 for driving a nail. Movement of the piston 26 is arrested by an air-cooled bumper 70 to thereby provide a cushioning effect. As illustrated in FIGS. 2 through 5 of this patent, the bumper 70 comprises an upper end 100, a lower end 102, an inner peripheral surface 104, and an outer peripheral surface 106. The bumper 70 has an annular flange 108 extending outwardly at its lower end 102. The annular flange 108 fits into the annular recess 82 in the cylindrical wall 24, when the bumper 70 is fitted within the cylinder 20, so as to secure the bumper 70 against the end wall 24. The bumper 70 has eight slots 110 extending radially from the inner peripheral surface 104 and eight slots 112 extending radially from the outer peripheral surface 106. Arrangement of the slots 110 and 112 in the bumper 70 provides a food bumping effect. However, since the bumper 70 is made of a single resilient or elastomeric material, the face of the bumper 70 that is subject to impact of the piston 26 would become soft and thus lose its impact-resisting effect. In addition, breakage tends to occur between the slots 112 and the slots 110. Further, when the upper end 100 of the bumper 70 is subject to the impact from the piston 26, the bumper 70 is already in intimate contact with the cylinder 20 and thus has a low cushioning effect, as there is no room allowing further deformation of the bumper 70. Further, during assembly of the bumper 70, the slots 112 of the bumper 70 must be aligned with the ports 80 in the cylinder 20 in order to assure exhaustion of the air in the space 30 below the piston 26 via the ports 80. Difficulty and inconvenience in the assembly procedure are thus caused.
An object of the present invention is to provide an abrasion-resistant bumper for a nail-driving tool comprising a cylinder defining a chamber for reciprocatingly receiving a piston. The bumper comprises a first bumper section and a second bumper section made of a material having a rigidity different from that of the first bumper section. When in a driving stroke of the piston toward the bumper, air in the chamber exits the cylinder via ports of the cylinder.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.